The object is to move 2 matches to get the cherry outside the glass. At the finish, the glass may be turned in any direction, but it must be exactly the same shape as before.

http://www.puzzles.com/PuzzlePlayground/OutOfGlass/OutOfGlass.htm

Move only three matches so that the bat will fly in another direction.

http://www.puzzles.com/PuzzlePlayground/TheBat/TheBat.htm

The Christmas Tree shown in the illustration contains exactly three equilateral triangles.

The object is to move three matches so that to get four equilateral triangles.

http://www.puzzles.com/PuzzlePlayground/ChristmasTree/ChristmasTree.htm

When the centres of any three coins lie in the corners of an equilateral triangle of some size, such coins form an equilateral coin triangle. How many equilateral coin triangles of different sizes can you count in the figure?

The object of the puzzle now is to remove the minimum number of coins so that no equilateral coin triangles remain. In other words, centres of any three coins among those that remained don't lie in the corners of an equilateral triangle.

http://www.puzzles.com/PuzzlePlayground/CoinsAndTriangles/CoinsAndTriang...

Students use the concept of Venn Diagrams to place each animal in the correct enclosure.
http://pbskids.org/cyberchase/games/logic/

Two mind reading activities. The first one can be explained using knowledge of linear expressions, while the second one is just a bit of fun.

A triangle is made up of four pieces. Move the pieces around to make a new congruent triangle. Except the new triangle is missing one square unit! Where did it go?

Your calculator is missing some of its keys! Which answers can you still get?
Six levels, from easy to challenging!

Alphametics are arithmetic puzzles in which each letter represents a different digit. Use your knowledge of place value and numbers to solve the puzzle.

This is a very cool and very engrossing set of puzzles. Use the cubes to build the shape that has the correct front, top and side views. Now try to solve the puzzle using the minimum number of cubes. The shape can be spun in 3-dimensions. Three thumbs up!

http://www.fi.uu.nl/toepassingen/02015/toepassing_wisweb.en.html